1. Field of the Invention
The present invention relates to a function simulation method and an apparatus therefor and, more particularly, to simulation method and apparatus which are suitable for function simulation of an asynchronously and parallel operative distributed system. In this simulation method, moreover, a Petri net model conducts the simulation of a function to transform the input data into the output data of the system.
2. Description of the Prior Art
There has not yet been established a method which is suitable for simulating the functions of an asynchronous self-controlled distributed system rather than a synchronous system.
The Petri net, a numerical model for describing and analyzing the flow and control of data in an asynchronous, parallel system, was proposed by Petri in 1962. 43 The Petri net model has been widely used and studied. See "Spectral Feature `Putting Petri nets to Work`" (by Tilak Agerwala, IEEE, Computer, December 1979, pp. 85 to 94).
Petri nets are expressed by an oriented graph which has two kinds of nodes, i.e., places and transitions. Arcs are oriented from the places to the transitions or vice versa. The places have tokens, and the arrangement of these tokens are called the "markings" of the Petri net model, the first of which is called the "initial marking" of the Petri net.
When a system is to be simulated by a Petri net model, the passage of the token through the transition means that data is processed and output. The token indicates data movement, but it does not indicate which data structure has been transformed nor does it indicate what structure it has been transformed into. This has the obvious disadvantage that data transforming procedures which are crucial in the simulation of functions are left undisclosed.